Display devices using a novel light source such as a light emitting diode (LED) and an organic light emitting diode (OLED) have been spotlighted and rapidly replaced existing display devices adopting typical light sources. Such display devices include various components such as a reflector, a reflector cup, a scrambler, a housing, and the like. Materials for such components are required to endure high temperature while minimizing deterioration in reflectance and white index due to a yellowing phenomenon.
As engineering plastics, polyesters, copolymers or blends thereof exhibit useful properties in terms of thermal resistance, impact resistance, processability, and the like, and are applied to various fields including materials for interior and exterior components.
A polyester resin is used as a material for display devices. As a polyester-based thermoplastic resin for display devices, a high thermal resistance polyester resin has not only merits such as no deformation at high temperature and good discoloration resistance, but also a problem of low impact resistance. In order to address this problem, although a polysiloxane compound may be added to the polyester resin to improve impact resistance, this method causes a problem of deterioration in processability such as bleeding out and the like when a large amount of the polysiloxane compound is added to the resin.
U.S. Pat. No. 7,009,029 discloses a polyamide resin composition which includes additives such as a photostabilizer in order to enhance photostability and discoloration resistance of the resin composition and exhibits good thermal resistance and reflectance. However, this polyamide resin composition suffers from deterioration in mechanical properties due to the additives and has difficulty securing long-term photostability and reliability.
Therefore, there is a need for a polyester-based thermoplastic resin that has good mechanical strength and high thermal resistance so as to be applied to a material for display devices and exhibits improved photostability and discoloration resistance without suffering from deterioration in impact resistance and processability.